libvirt: parse alias out from device config

Libvirt assigns a device alias for each device in the domain and uses
this identifier in the events related to these devices, like device
detach.

This patch extends the LibvirtConfigGuestInterface and the
LibvirtConfigGuestDisk config object to parse the alias back from the
domain config. The alias is intentionally not used during domain XML
generation as it is expected that libvirt will populate and persist
this field.

This is part of the longer series trying to transform the existing
device detach handling to use libvirt events.

Change-Id: I16e7df6932bb7dff243706ee49338ba6b3782085
Related-Bug: #1882521

nova/tests/unit/virt/libvirt/test_config.py

@@ -2285,6 +2285,21 @@ class LibvirtConfigGuestInterfaceTest(LibvirtConfigBaseTest):
         self.assertNotIsInstance(obj.device_addr,
                              config.LibvirtConfigGuestDeviceAddressDrive)
 
+    def test_config_interface_alias(self):
+        xml = """
+            <interface type='network'>
+                <mac address='52:54:00:14:6f:50'/>
+                <source network='default' bridge='virbr0'/>
+                <target dev='vnet0'/>
+                <model type='virtio'/>
+                <alias name='net0'/>
+            </interface>"""
+
+        obj = config.LibvirtConfigGuestInterface()
+        obj.parse_str(xml)
+
+        self.assertEqual('net0', obj.alias)
+
 
 class LibvirtConfigGuestFeatureTest(LibvirtConfigBaseTest):
 
@@ -2813,6 +2828,21 @@ class LibvirtConfigGuestSnapshotTest(LibvirtConfigBaseTest):
 
         self.assertTrue(obj.driver_iommu)
 
+    def test_config_alias_parse(self):
+        xml = """
+            <disk type="file" device="disk">
+              <source file="/tmp/hello.qcow2"/>
+              <target bus="virtio" dev="/dev/sda"/>
+              <serial>7a97c4a3-6f59-41d4-bf47-191d7f97f8e9</serial>
+               <alias name='virtio-disk0'/>
+            </disk>"""
+        xmldoc = etree.fromstring(xml)
+
+        obj = config.LibvirtConfigGuestDisk()
+        obj.parse_dom(xmldoc)
+
+        self.assertEqual('virtio-disk0', obj.alias)
+
 
 class LibvirtConfigNodeDeviceTest(LibvirtConfigBaseTest):
 

nova/virt/libvirt/config.py

@@ -1037,6 +1037,7 @@ class LibvirtConfigGuestDisk(LibvirtConfigGuestDevice):
         self.boot_order = None
         self.mirror = None
         self.encryption = None
+        self.alias = None
 
     def _format_iotune(self, dev):
         iotune = etree.Element("iotune")
@@ -1246,6 +1247,8 @@ class LibvirtConfigGuestDisk(LibvirtConfigGuestDevice):
                 e = LibvirtConfigGuestDiskEncryption()
                 e.parse_dom(c)
                 self.encryption = e
+            elif c.tag == 'alias':
+                self.alias = c.get('name')
 
 
 class LibvirtConfigGuestDiskBackingStore(LibvirtConfigObject):
@@ -1688,6 +1691,7 @@ class LibvirtConfigGuestInterface(LibvirtConfigGuestDevice):
         self.vlan = None
         self.device_addr = None
         self.mtu = None
+        self.alias = None
 
     def __eq__(self, other):
         if not isinstance(other, LibvirtConfigGuestInterface):
@@ -1914,6 +1918,8 @@ class LibvirtConfigGuestInterface(LibvirtConfigGuestDevice):
                 self.device_addr = obj
             elif c.tag == 'mtu':
                 self.mtu = int(c.get('size'))
+            elif c.tag == 'alias':
+                self.alias = c.get('name')
 
     def add_filter_param(self, key, value):
         self.filterparams.append({'key': key, 'value': value})